Since he joined Romney's campaign as foreign affairs spokesman, many of Grenell's most provocative musings on Twitter have been deleted in a cleanup that is the latest reminder of how social media has become a sideshow - and at times more - in the 2012 campaign.

In an email, Grenell, who was spokesman for the U.S. mission to the United Nations during George W. Bush's presidency, acknowledged to Reuters that he began removing messages from Twitter after their content was reported by Politico on Friday.

Before then, Grenell had been an acerbic observer on Twitter of a wide range of political figures and topics.

Besides the first lady, Democrats who were targets of Grenell's more pointed tweets included President Barack Obama, the Obamas' daughter Malia, Vice President Joe Biden and various members of the media, many connected to NBC or its liberal-leaning cable affiliate, MSNBC.

But many of Grenell's most biting Twitter messages were directed at fellow Republicans.

According to an account posted on a Politico blog the day after Grenell joined Romney's campaign, he was a particularly sarcastic tweeter during some of the televised debates for Republican presidential candidates earlier this year. Grenell targeted Gingrich and his third wife, Callista, over their appearance and Newt Gingrich's turbulent marital history.

Among Grenell's tweets about Newt Gingrich, a former U.S. House speaker, was this missive in January: "what's higher? The number of jobs newt's created or the number of wives he's had?"

And in an apparent reference to Gingrich's weight, Grenell mused in January: "i wonder if newt has investments in Lipitor," referring to a cholestoral-lowering drug.

Regarding Romney, his future boss, Grenell was a little friendlier, tweeting in January that the former Massachusetts governor "wasn't my 1st choice but he's gonna be the nominee. He will need your vocal support."

Before he scrubbed his Twitter postings, Grenell had tweeted 7,577 times, according to a screen shot taken last Friday by the Huffington Post. As of Monday, Grenell's Twitter feed listed 6,762 tweets.

"My personal twitter feed was written before I joined the Romney campaign," Grenell said in a statement. "Some tweets were meant to be tongue-in-cheek and humorous. Regrettably, I can now see how they can also be hurtful. I didn't mean them that way and removed them from twitter. I sincerely apologize for any hurt they caused," Grenell added.

A spokesman for Gingrich's campaign declined to comment.

Romney campaign officials referred inquiries about Grenell's activity on Twitter to his statement. Campaign spokeswoman Andrea Saul did not respond to questions about whether the campaign would distance itself from Grenell's comments on Twitter.

'THE ETHOS' OF A CAMPAIGN

Kathleen Hall Jamieson, an expert on political communications at the University of Pennsylvania's Annenberg School, said it was puzzling that Romney's campaign would hire as an official mouthpiece someone with a history of posting aggressive and personal comments on the Web.

She said it was "not clear why the Romney campaign would take on an operative with the rhetorical tendencies evident in the now-suppressed postings.

"Campaign managers and spokespersons contribute to reporters' sense of the ethos of a campaign and occasionally of the candidate," Jamieson said. "The best are thoughtful, informed and make a cogent case for the candidate. Those who overstep are often dismissed."

Grenell's Twitter commentary on Democrats included a series of unflattering remarks about the Obamas. "Without a teleprompter, Oh-bahh-mahhh isss ahhh slowww and weakkk speakerrrr ahhhh...#syria" Grenell tweeted last December.

"Hating people who make more than you is the product of having a community organizer as president. #AnyoneButObama", Grenell tweeted in January.

Among his numerous postings about Michelle Obama was this item from early April: "did you notice that while Michelle Obama is working out on the (TV show) BiggestLoser she is sweating on the East Room's carpet ? Just saying...."

Grenell retweeted the word "Wow" to someone else's posting about Malia Obama taking a Spring Break trip to Mexico with friends. Later in March he tweeted: "the media outlets that aren't reporting on the first daughter should remember that when obama talks about them on the campaign trail."

A representative of the Obama campaign said it would have no comment.

In other tweets, Grenell suggested that Biden had undergone treatment with Botox. He also posted numerous attacks on journalists and programs who write for or appear on liberal media outlets, including NBC veterans Andrea Mitchell, Chuck Todd and Tom Brokaw, and suggested that ABC stood for: "All Barack's Cronies."

Aside from Grenell's tweets, the Wikipedia entry on him was trimmed significantly earlier this year to remove extensive detail on Grenell's apparent connections in the political and business world.

Grenell said that did not know who edited his Wikipedia entry, but did acknowledge "making minor changes" in the posting last year.